The present invention relates to the scheduling of movement of plural units through a complex movement defining system, and in the embodiments disclosed, to the scheduling of the movement of freight trains over a railroad system utilizing route protection.
Systems and methods for scheduling the movement of trains over a rail network have been described in U.S. Pat. Nos. 6,154,735, 5,794,172, and 5,623,413, the disclosure of which is hereby incorporated by reference.
As disclosed in the referenced patents and applications, the complete disclosure of which is hereby incorporated herein by reference, railroads consist of three primary components (1) a rail infrastructure, including track, switches, a communications system and a control system; (2) rolling stock, including locomotives and cars; and, (3) personnel (or crew) that operate and maintain the railway. Generally, each of these components are employed by the use of a high level schedule which assigns people, locomotives, and cars to the various sections of track and allows them to move over that track in a manner that avoids collisions and permits the railway system to deliver goods to various destinations.
As disclosed in the referenced patents and applications, a precision control system includes the use of an optimizing scheduler that will schedule all aspects of the rail system, taking into account the laws of physics, the policies of the railroad, the work rules of the personnel, the actual contractual terms of the contracts to the various customers and any boundary conditions or constraints which govern the possible solution or schedule such as passenger traffic, hours of operation of some of the facilities, track maintenance, work rules, etc. The combination of boundary conditions together with a figure of merit for each activity will result in a schedule which maximizes some figure of merit such as overall system cost.
As disclosed in the referenced patents and applications, and upon determining a schedule, a movement plan may be created using the very fine grain structure necessary to actually control the movement of the train. Such fine grain structure may include assignment of personnel by name as well as the assignment of specific locomotives by number, and may include the determination of the precise time or distance over time for the movement of the trains across the rail network and all the details of train handling, power levels, curves, grades, track topography, wind and weather conditions. This movement plan may be used to guide the manual dispatching of trains and controlling of track forces, or provided to the locomotives so that it can be implemented by the engineer or automatically by switchable actuation on the locomotive.
The planning system is hierarchical in nature in which the problem is abstracted to a relatively high level for the initial optimization process, and then the resulting course solution is mapped to a less abstract lower level for further optimization. Statistical processing is used at all levels to minimize the total computational load, making the overall process computationally feasible to implement. An expert system is used as a manager over these processes, and the expert system is also the tool by which various boundary conditions and constraints for the solution set are established. The use of an expert system in this capacity permits the user to supply the rules to be placed in the solution process.
In prior art movement planners, plans are periodically generated which result in an optimized planned movement of the trains. Typically, the actual movement of the trains is monitored in some manner, and if deviations to the planned movement occur, a replanning cycle occurs to make modifications to the movement plan to account for the deviations.
One problem with the typical optimizing movement planner is that because the railroad environment is dynamic, the detailed plan for a train (e.g., it's meet and pass locations) may change each time the movement plan is calculated. While the changed route for a train may be optimal in some sense, changes to the movement plan for a train are undesirable operationally if they affect the route immediately ahead of the train. For example, the planner may have planned a specific train meet, and the dispatcher may have taken actions in reliance on the planned train meet. If the meet is changed at the last minute due to the calculation of a marginally better plan, the dispatcher may not have sufficient time to react to the new train meet and the undisclosed plans of the dispatcher may be disrupted.
This problems stems from the movement planner continually striving to produce the most optimum movement plan. However, if multiple routes are almost equally optimal, the slightest environmental change may cause the planner to shift from one route to the other route, resulting in thrashing, i.e., the repeated change back and forth between alternate routes. This is very problematic for the dispatcher who may need to take specific actions based in the route chosen.
Thus, while last minute route changes are desirable when they result in a clearly superior alternate, i.e., the previous route has become impassable due to a track block, plan changes immediately head of the train for a nominally optimal route are clearly undesirable.
The present disclosure avoids these problems found in the prior art by protecting the route immediately ahead of a train to avoid trashing that would otherwise occur.